For example, Patent Document 1 discloses a labyrinth seal for inhibiting leakage of fluid passing from the high-pressure side to the low-pressure side through a gap between a rotating body and a stationary body that configure a rotary machine. This labyrinth seal mainly includes a step structure formed on an outer circumferential surface of the rotating body and fins provided on an inner circumferential surface of the stationary body.
FIG. 7 is a schematic cross-sectional view showing a conventional labyrinth seal. According to the labyrinth seal of Patent Document 1, as shown in FIG. 7, a flow P of the fluid passing from the high-pressure side to the low-pressure side through a gap between an outer circumferential surface of a rotating body 101 and fins 103, 104 provided on an inner circumferential surface of a stationary body 102 is generated. At this time, a large vortex V1 is formed between the fin 103 on the high-pressure side and the fin 104 on the low-pressure side, and a small vortex V2 is formed on the side of a step 101a. Then, fluid friction is generated in the vortices V1 and V2 and therefore energy loss occurs; thereby, the fluid leakage can be inhibited.